Chronic migraine with and without medication overuse: experience in a hospital series of 434 patients.

INTRODUCTION Chronic migraine (CM) is a complication of episodic migraine, favored by risk factors as medication overuse (MO). We intend to compare demographic and clinic characteristics of a series of CM patients, with and without MO. METHODS The study included patients with CM (2006 revised criteria) attended in a headache outpatient office located in a tertiary hospital between January 2008 and May 2012. We recorded demographic characteristics, age at migraine onset, time from onset, previous use of symptomatic or preventive therapy, and headache impact measured with six-item headache impact test (HIT-6). RESULTS A total of 434 patients (357 women, 77 men) were diagnosed with CM out of the 1868 (23.2%) that attended our clinic. Of these, 258 (72.2%) fulfilled criteria of MO, and 59.8% of those with MO, and 41.1% of cases without MO had previously received preventative treatment (P<.001). Age at onset of migraine was lower in MO patients (21.2±10.1 vs 23.8±12.5 years, P=.02) and time from onset to headache clinic consultation was higher in MO cases (23.8±14.1 vs 18.3±14.8 years, P<.001). We found no difference between both groups in average HIT-6 score and the percentage of patients with a HIT-6 score over 55. CONCLUSIONS CM, with or without MO, is a burdensome group of patients in our headache clinic. Patients with MO are referred later and have more frequently received preventive treatments.